Mitsubishi Repair: Low idle and stalling, mitsubishi eclipse, electrical load

Question
Anthony,
    Thanks for the advice.  I repalced the IAC and things have improved some.  The car no longer surges uncontrolable at idle.  Now I have a new problem, or maybe the same one, but it was just hiding under a faulty IAC.  Whenever an electrical load (A/C compressor, second cooling fan, even headlights) is applied at idle the RPM drop from 800 to 500.  A second later the idle is back up to 800.  I noticed this while waiting in a drive thru line.  When the second fan kicked in the idle dropped, then rose back up.  What could cause this delay?  The alternator and battery are new.  Any suggestions?

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Followup To
Question -
I have a 1994 Mitsubishi Eclipse 1.8L manual transmission.  I am having trouble with a low idle speed.  When I am stopped and the A/C is on the idle is very erratic, it bounces from <400 rpm to >1500 rpm.  It will very quickly stall if I don't give it some gas.  It seems to work fine with the A/C off.  The alternator is brand new and i still have this problem.  I heard that there is a TSB on the Idle Air Control, is this my problem, or is something else wrong?

Thanks
Answer -
Glenn,
The most common cause for your problem is a malfunctioning Idle Air Control (IAC) motor.  Your problem is commonly called "idle surge".  When running the A/C, your engine will have an extra load on it.  And with extra load, that will slow down your engine and the idle.  Your IAC is responsible for raising your idle speed, and holding it constant regardless of the load applied to your engine.  When you IAC is faulty, it will be unable to control the idle speed.  Have your IAC checked and replaced if it's malfunctioning.
Good luck!

Answer
Glenn,
This is 100% normal.  Now that you have a new IAC installed, it's able to do it's job correctly.  800 RPM is the factory specification your idle should be at.  When the additional load of the A/C, second fan, headlights, etc., come on, your alternator must work extra hard to keep the voltage and current to the correct levels.  With the extra strain, your RPMs will dip down to 500.  Your car's computer will recognize this, send the signal to the IAC to correct the lowered RPMs, and your IAC can now correct the problem by bringing it back up to 800 RPMs.  You may even notice your idle increases above 800 when shutting off your A/C or headlights.  If it then settles back down to 800 RPMs, that is good.  As long as your car's RPMs no longer go out of control while idiling, you should be fine.
Good luck!